Hard disk drives are used in almost all computer system operations, and recently even in consumer electronic devices such as digital cameras, video recorders, and audio (MP3) players. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago. The hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that can spin at a wide range of standard rotational speeds depending on the computing application in which the hard disk drive is being used. Commonly, the central core is comprised, in part, of a spindle motor for providing rotation of the hard disks at a defined rotational speed. A plurality of magnetic read/write transducer heads, commonly one read/write transducer head per surface of a disk, where a head reads data from and writes data to a surface of a disk, are mounted on actuator arms.
Data is formatted as written magnetic transitions (information bits) on data tracks evenly spaced at known intervals across the disk. An actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly at the extreme of the actuator arm, e.g., the suspension and magnetic read/write transducer head, is known as a head gimbal assembly (HGA).
In operation, pluralities of hard disks are rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the actuator arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk drive aligns a head, via the actuator arm, over the specific track location and the head writes the information to the disk.
Particularly, the data, the read/write head, and the hard disk are vulnerable to loss and/or damage during read/write operations. During a read/write operation, the read/write head is in very close proximity to the surface of the hard disk. If the hard disk is exposed to a shock or force during a read/write operation, the read/write head can contact the surface of the hard disk. This impact can cause loss of data being accessed or loss of data being written to the hard disk. An impact between the read/write head and the surface of the hard disk can also cause damage to the read/write head and/or the surface of the hard disk. In many instances, the read/write head and/or the hard disk, or portions thereof, are rendered useless due to damage caused by the impact.
Accordingly, solutions comprised of mechanisms and/or protective measures have been developed for preventing such damage. These measures can include; causing an unload which is removing the head from close proximity of the hard disk thus preventing head contact with data surface of the hard disk, braking which halts the rotation of the hard disk, parking which places the read/write head in proximity to a predefined sector or track of the hard disk that is configured to not hold data, and the like. While hard disk drives implemented in certain types of computer systems, e.g., desktop, workstation, servers, and the like, are less likely to be subject to an external shock or force than hard disk drives implemented in those computer systems designed for mobility, e.g., laptops, mini computers and the like, it is common for these mechanisms and measures to be utilized in most hard disk drives, regardless of the computer system into which they are to be implemented.
One solution, as described in U.S. Pat. No. 5,227,929 to Comerford, and as shown in FIG. 9 (Prior Art), is to utilize an accelerometer 50, mounted to the frame within a hard disk drive 11, communicatively coupled to a dedicated processor 51. Hard disk drive 11 is generally comprised of one or more magnetic disks, a read/write head for each surface of each magnetic disk, an actuator arm from which each read/write head extends, a central core for rotating the disk, a motor for maneuvering the read/write heads over a particular section of the magnetic disk, and circuitry for enabling proper function of the hard disk drive.
The accelerometer 50 provides output signals for each of the three axes, e.g., X, Y and Z, to dedicated processor 51. Dedicated processor 51 continuously monitors the acceleration signals, computes the resultant acceleration vector and compares the scalar magnitude of the acceleration vector with a preset range of values. The preset range represents an acceleration that would suggest and impending impact. When such an event occurs, the dedicated processor 51 then directly signals controller 19, or alternatively signals the central processing unit (CPU) 2 of the computer system 1, in which hard disk drive 11 is implemented, which then signals controller 19, to cause a parking of the disk heads and/or a stoppage of the rotation of the disk.
While this solution may provide a measure of protection, it is not without drawbacks. A major drawback to an accelerometer is the cost. Currently, the cost of an accelerometer is estimated to be approximately three dollars (US). Another drawback is that the accelerometer 50 is to be mounted within the hard disk drive housing. By virtue of the continued miniaturization of a hard disk drive, particularly with regard to newer low profile hard disk drives, an accelerometer 50 can utilize excessive real estate within the housing such that continued miniaturization can be limited, delayed and/or prevented. In some instances, currently available accelerometers are of such size that they do not comply with the form factor of low profile or miniature hard disk drives. Another drawback is that an accelerometer 50 requires a dedicated processor 51 which, along with the accelerometer, can also utilize excessive real estate and both of which can require additional power. When implemented in a portable computing system that does not have an unlimited power supply, e.g., a laptop computer, these additional components, e.g., accelerometer 50 and dedicated processor 51, can have a detrimental effect on the limited power supply contained within the portable computer system. Another drawback is that to implement the accelerometer 50 and the dedicated processor 51, significant alterations to existing wiring and their related connections are performed to enable proper hard disk drive functionality as well as the proper functioning of the accelerometer and the dedicated processor.
Therefore, what is needed is a way to detect an external force applied to a hard disk drive while utilizing information obtained from existing components and structures within a hard disk drive.